Comb dynamics in photonic crystal microresonators with built-in nonlinear optical isolator on single-layer deposited silicon nitride

Nonlinear frequency generation is demonstrated in silicon nitride photonics using microring resonators with engineered dispersion through a Bragg grating perturbation. The processes by which these nonlinear effects occur introduces backscattered light, due to bidirectionally-propagating hybridized modes. Such backscattered light is often detrimental to the pump laser and imposes a limit on the power that can be delivered to the ring system, reducing the operating range of ring resonators for nonlinear light generation. We mitigate these effects with an on-chip passive optical isolator, which protects the pump laser from backscattered light, allowing for higher pump power operation regimes. Furthermore, we introduce a recycling channel that allows for power to be re-pumped into the mirroring resonator to enable controllable exploration into more interesting nonlinear optics phenomena.